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NMR and MRI from Physical Concepts to Medical Applications

Oscar Bernal

California State University

Los Angeles

U Nacional, Bogota

Outline

Nuclear Magnetic Resonance The idea of imaging (MRI) In-Vivo NMR Spectroscopy Some recent trends/advances Prospects

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Nuclear Magnetic Resonance

What’s in the name? Main historical developments

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NuclearH2O

1 cm

~ 3 x 1022 molecules

3 x 108 cmO

HH

Properties:* mass* charge* spin

Nucleus ~1013 cm

1 x 108 cme

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Magnetic

Interaction:

E . H )

Applied Magnetic Field H

S

N

HMagnetic Moment

HH2O

Precession: H

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Resonance

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Resonance

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Receiver

NMR Experiment

Generator

S

N

H

Low Mid High Frequencies

SignalIntensity

H

NMR Spectrum

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The Beginning

I. I. Rabi: Molecular beam experiments, measurement of atomic/nuclear magnetic moments by a “resonance method” 1937 Nobel prize awarded 1944

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First Successful Detection(s) in Bulk Matter

Felix Bloch (Stanford)“Nuclear Induction”

January 1946

Edward Purcell (MIT)“Resonant Absorption”

December 1945

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Some Fields of Application

Physics/Materials Science Chemistry/Bio-chemistry Medicine/Physiology/Radiology Geology Agricultural/Soil Sciences Food Technology Defense/Forensics

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Main Developments Bloch, Purcell: First successful detection(s) 1945;

Nobel Prize awarded 1952 Henry Torrey: rf-pulse applications 1949 Erwin Hahn: Spin echo 1949 Walter Knight: Knight Shift 1949 W.G. Proctor & F.C. Yu: Chemical shift 1950 Arnold, Dharmatti, Packard: High Resolution 1951

Two decades of chemistry applications followed

“Chemists got the point very quickly, thanked the physicists and took over” Packard 1963

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Main Developments (contd.)

Raymond Andrew: Magic Angle Spinning 1960 Richard Ernst, Wes Anderson: FT NMR 1965;

Nobel Prize awarded to Ernst 1991 The Minicomputer becomes available: 1965 J.W. Cooley & J.W. Tukey: FFT algorithm 1965 Jeener/Muller/Kumar/Ernst : 2D-NMR 19711975 Quad-PD & David Hoult’s CYCLOPS method 1975 Kurt Wüthrich: 3D structure of bio-molecules in

solution 1980’s; Nobel Prize awarded 2002

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Application to Physical Sciences

T TN : Antiferromagnetic

S

N

H 0

T TN

Resulting spectrumExperiment: Detection of AFM

T TN : Paramagnetic

0 0

T TN

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MRI: The Idea

xx1 x2 x3 x4

S

N

S

N

S

N

S

N

H1

H2

H3

H4

1 2 3 4

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1 2MRI

H ( x)

xx1 x2

H2

H1

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Major MRI Developments Raymond Damadian: T1/T2 longer

in cancer cells 1971 (diagnosis/radiology)

Paul Lauterbur, Peter Mansfield: use of gradients for imaging and mathematical tools for image production 1971; Nobel Prize awarded 2003

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MRI and Nuclear RelaxationNormal Abnormal

Precession time

Inte

nsi

ty

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MRI and Nuclear RelaxationNormal Abnormal

Precession time

Inte

nsi

ty

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MRI Scan

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In-Vivo Spectroscopy

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Trends

MRI Assisted SurgeryPatient Comfort

Functional MRI

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Surgery Robot (AIST-Japan)

Stand-up MRI (Fonar-USA)

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Prospects

Higher Magnetic Fields High-Temperature SC Coils Faster Acquisition (computers) Imaging Processing Procedures Single Nucleus Detection Nuclear Polarization Enhancement